Distance fields

I am working on a large project in which I need to have faithful distance fields given a set of points.
I was thinking to use a well known method which is to place the tip of a cone at each point (with the axis of the cone parallel to the view axis and the cones enlarging away from the camera - also the height of the cone and the radius must be the same).
I would like to “read” the distance field out of the z-buffer but I am concerned that projection calculations and near-plane and far-plane will make this impossible because of non-linear transformation on the correct values.
Is it possible, maybe to use ortho? or am i gonna loose the “distance” value?
Any advice?



I’m not very familiar with distance fields - what is the general idea? do you need the distance to each point in a 2d plane given a viewpoint? are you calculating a distance fields to a 3d volume?